Cigarette smoke linked to breast cancer

University of Florida scientists have reported that cigarette smoke could turn normal breast cells cancerous by blocking their ability to repair themselves, eventually triggering tumour development.

In the study, researchers exposed normal breast epithelial cells to cigarette smoke condensate-a tar and found the cells acquired the mutation characteristics of malignant cells.

The researches found that DNA repair was compromised when chemical components of smoke activate a key gene. That gene interacts with an enzyme that plays a crucial role in repairing damaged DNA, preventing it from doing its job. The cell, despite its mutated form, can then multiply rapidly, triggering a tumour.

A cell with damaged DNA has one of two fates, said Satya Narayan, Ph.D., an associate professor of anatomy and cell biology at UF's College of Medicine.

"Its DNA repair machinery can be enhanced and it can fix the damaged DNA and restore genomic stability, or if the DNA repair machinery becomes compromised within the cell, then it can lead to an accumulation of mutations because the DNA is not fixed before the cell begins to divide. The mutation then becomes a permanent part of the genome and causes genomic instability, and genomic instability can bring about several cellular dysfunctions, and one of them can lead to tumour formation," he said.

In general, about two-thirds of these cells will be growth-retarded, and some actually acquire cancer-like characteristics, he said.

"Some of these cells that survive are really acquiring true mutagenic characteristics," Narayan said. "A defect in only one cell is important for growth of a full-blown tumour. You don't need 1,000 or 1 million cells to be affected. Only a single cell which may have genomic instability due to compromised DNA repair capacity of the cell can be sufficient for a tumour to develop. That has to be considered also when we do these kinds of studies."

Narayan said the next step will be to find ways to manipulate cells' capacity for DNA repair and to prevent tumour formation.